Tilt-up structures design is a rapidly growing method of construction, with approximately 300 million square feet of concrete panels being constructed in the U.S. each year (Palmer, n.d.). Just as its name indicates, this construction method involves fabricating concrete panels and tilting them up and into place to create the exterior of a structure.
One of the biggest challenges for structural engineers while designing tilt-up buildings is ensuring that all walls are braced properly. The walls are often tall, thin, and heavy and therefore do not have much stability in the weak axis. Historically, one of the most common issues for tilt-up buildings has been the walls detaching from roofs. It is important to properly design and detail the anchorage of the walls to the roof to prevent them from falling over.
Careful planning is needed to use this complex construction process safely and efficiently, but that process can be broken down into three simplified phases: design, construction, and lifting.
Design
Tilt-up walls are designed to be as thin as possible while still being strong enough to support the roof and floors in addition to lateral loads from wind and earthquakes. Wall thickness and reinforcing steel design are dependent on the roof height and the location of doors and windows. These factors are carefully considered during the design phase.
Construction
After the concrete foundation is poured and hardened, typically through the slab-on-grade style, wood forms are set on top of the slab in the shape of each wall panel. Reinforcing steel bars and lifting inserts are then placed within the wood forms before the concrete is poured to create the wall panels.
Lifting
Once the wall panels are hardened, a crane is attached to the lifting inserts and slowly tilts up each wall panel. The crane then moves each wall panel to its final location, where it is held in place with diagonal braces until the roof construction is complete.
The Benefits of Tilt-Up Construction
While tilt-up construction can be used on any project, it is particularly useful when clients are facing a tight schedule or want to minimize future maintenance. This method is also beneficial when the project includes a structure with a large amount of square feet, such as a warehouse or school. On these larger projects, tilt-up construction methods can provide great value as compared to traditional methods. This method typically leads to faster construction timelines since it eliminates much of the finishing steps associated with traditional vertical walls.
Another advantage lies in the small number of personnel needed to complete tilt-up construction – smaller teams equal lower labor costs. Additionally, from a long-term perspective, tilt-up construction offers superior fire and weather resistance, leading to lower insurance premiums.
Sustainability
Sustainability and green building are big topics of conversation in the architecture, engineering, and construction industry. While there is no end-all-be-all solution to preventing environmental impacts during the project process, tilt-up construction holds environmental benefits and provides sustainable building practices in several ways.
Tilt-up construction produces less overall waste and does not require as many materials, and much of the building materials and processes can be acquired locally, reducing the need for transporting equipment and materials. The reinforced concrete panels also provide incredible insulation, resulting in energy efficiency over the lifetime of the building.
Additionally, the life span of a building constructed using the tilt-up method is superior to structures built using traditional construction methods. While traditional buildings typically wear out or degrade beyond the ability to maintain them within 15 to 30 years, tilt-up buildings can withstand more than 50 years of use with a very minimal maintenance profile. These factors, plus many more, make tilt-up a wonderful green building solution.
Tilt-Up Construction in Action: St. John Garabed Armenian Church
In 2021, Horrocks completed a tilt-up design for the St. John Garabed Armenian Apostolic Church in San Diego, California.
“The St. John Garabed Armenian Church was an extremely fun project to design. It showcases how tilt-up structures don’t have to all be the typical box style. The sky is the limit on what you can design utilizing the tilt-up method.” – James Sipes, PE, Lead Designer on the St. John Garabed Armenian Church Project
The exterior of the church was designed to look like a historic tone Armenian church. Horrocks’ design team replicated the stone look by forming grooves in the concrete to match a stone pattern. This building is unique because of the unusual shape of many wall panels, including curved panels, substantial arch openings, and large architectural recesses. The layout of the wall panels is also unique in that the panels are stacked on top of each other and span across the building to create the central tower at the center of the church while still incorporating a large gathering area below.
This project is a wonderful example of the creativity that can be achieved by utilizing a tilt-up structure’s design. The only limit is one’s imagination.
For more information about Horrocks' tilt-up design experience, email us at info@horrocks.com.
References
Palmer, B. (n.d.).Tilt Up Concrete. ConcreteNetwork.com.https://www.concretenetwork.com/tilt-up/#:~:text=The%20Tilt%2DUp%20Concrete%20Association,million%20square%20feet%20of%20space